System and Method for Separating Gaseous Material From Formation Fluids

ABSTRACT

There is provided a system for effecting production of formation fluids from a subterranean formation. The system includes a gas anchor for mitigating gas lock. Sealing engagement of the gas anchor against the wellbore tubular is effected without use of a conventional packer, which would otherwise be susceptible to receiving debris deposited from the formation fluid, which thereby results in the packer, as well as the gas anchor, becoming vulnerable to becoming stuck within the wellbore tubular.

FIELD

The present disclosure relates to production of formation fluids, and,in particular, separating gaseous material that is entrained within theformation fluids.

BACKGROUND

Gas lock is a problem encountered while producing wells, especiallywells with horizontal portions. Packer-type gas anchors are provided toremedy gas lock. However, packer-type gas anchors are relativelyexpensive. Further, the packers on packer-type gas anchors aresusceptible to having debris accumulate thereon and, as a result,becoming stuck within the wellbore tubular against which it forms aseal. This makes it difficult to remove production tubing from thewellbore, such as during a workover. Such attempt at removal may alsodamage the packer, thereby rendering the packer-type gas anchor unusablefor future production.

SUMMARY

In one aspect there is provided a system for effecting production offormation fluid from a subterranean formation, comprising:

a wellbore tubular disposed within a wellbore, wherein the wellboretubular includes a receptacle portion, wherein the receptacle portionincludes a receptacle sealing surface;a production tubular, disposed within the wellbore tubular, including:

a formation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing member-engaging surface portion;

a gas separator portion configured to co-operate with at least thewellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid;

a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and

a prime mover disposed for inducing flow of the formation fluid from asubterranean formation and into the formation fluid-receiving fluidpassage portion, and for receiving and energizing the gaseousmaterial-depleted formation fluid to flow through the gaseousmaterial-depleted formation fluid conducting-fluid passage portion tothe surface;

anda sealing member disposed between the sealing member-engaging surfaceportion and the receptacle sealing surface for effecting a seal betweenat least the sealing member-engaging surface portion and the receptaclesealing surface, for preventing, or substantially preventing, flow ofthe formation fluid between at least the sealing member-engagingexternal surface portion and the receptacle sealing surface;wherein the co-operation between the gas separator portion and at leastthe wellbore tubular is with effect that, while the flow of theformation fluid is being induced by the prime mover and received throughthe formation fluid-receiving fluid passage portion, flowing of thereceived formation fluid is directed through a gas separator annulusdisposed between the gas separator portion and the wellbore tubular, ina direction opposite to that which the formation fluid is flowing whilebeing received by the formation fluid-receiving fluid passage portion ofthe formation fluid-receiving conduit portion of the production tubular,prior to being received by the prime mover, and the formation fluidflowing through the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by the effected seal between at least the sealingmember-engaging surface portion of the formation fluid-receiving conduitportion of the production tubular and the receptacle sealing surface ofthe receptacle portion of the wellbore tubular, wherein, while theflowing of the received formation fluid is being directed through thegas separator annulus, the at least a fraction of the entrained gaseousmaterial becomes separated, in response to buoyancy forces, from thereceived formation fluid that is being directed through the gasseparator annulus;and wherein the receptacle sealing surface is disposed less than adistance “D” of 2.5 millimetres from the sealing member-engaging surfaceportion.

In another aspect there is provided a system for effecting production offormation fluids from a subterranean formation, comprising:

a wellbore tubular disposed within a wellbore, wherein the wellboretubular includes:

a casing string;

a liner string, coupled to the casing string, the liner stringincluding:

-   -   a polished bore receptacle that includes a receptacle portion,        wherein the receptacle portion includes a receptacle sealing        surface; and    -   a sealing surface, sealingly engaged to the casing string for        preventing, or substantially preventing, flow of formation fluid        between the sealing surface and the casing string; and        a production tubular, disposed within the wellbore tubular,        including:

a formation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing surface disposed in sealing engagement with thereceptacle sealing surface for preventing, or substantially preventing,flow of the formation fluids between the sealing surface and thereceptacle sealing surface;

a gas separator portion configured to co-operate with at least thewellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid;

a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and

a prime mover disposed for inducing flow of the formation fluid from asubterranean formation and into the formation fluid-receiving fluidpassage portion, and for receiving and energizing the gaseousmaterial-depleted formation fluid to flow through the gaseousmaterial-depleted formation fluid conducting-fluid passage portion tothe surface;

wherein the co-operation between the gas separator portion and at leastthe wellbore tubular is with effect that, while the flow of theformation fluid is being induced by the prime mover and received throughthe formation fluid-receiving fluid passage portion, flowing of thereceived formation fluid is directed through a gas separator annulusdisposed between the gas separator portion and the wellbore tubular, ina direction opposite to that which the formation fluid is flowing whilebeing received by the formation fluid-receiving fluid passage portion ofthe formation fluid-receiving conduit portion of the production tubular,prior to being received by the prime mover, and the formation fluidflowing through the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by at least the sealing engagement between thesealing surface of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular, wherein, while the flowing of thereceived formation fluid is being directed through the gas separatorannulus, the at least a fraction of the entrained gaseous materialbecomes separated, in response to buoyancy forces, from the receivedformation fluid that is being directed through the gas separatorannulus.

In another aspect there is provided a system for effecting production offormation fluids from a subterranean formation, comprising:

a wellbore tubular disposed within a wellbore, wherein the wellboretubular includes a casing, wherein the casing includes a receptacleportion, wherein the receptacle portion is defined by an inwardlyextending protrusion of the casing and includes a receptacle sealingsurface; anda production tubular, disposed within the wellbore tubular, including:

a formation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing surface disposed in sealing engagement with thereceptacle sealing surface for preventing, or substantially preventing,flow of the formation fluids between the sealing surface and thereceptacle sealing surface;

a gas separator portion configured to co-operate with at least thewellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid;

a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and a prime mover disposed for inducing flow of theformation fluid from a subterranean formation and into the formationfluid-receiving fluid passage portion, and for receiving and energizingthe gaseous material-depleted formation fluid to flow through thegaseous material-depleted formation fluid conducting-fluid passageportion to the surface;

wherein the co-operation between the gas separator portion and at leastthe wellbore tubular is with effect that, while the flow of theformation fluid is being induced by the prime mover and received throughthe formation fluid-receiving fluid passage portion, flowing of thereceived formation fluid is directed through a gas separator annulusdisposed between the gas separator portion and the wellbore tubular, ina direction opposite to that which the formation fluid is flowing whilebeing received by the formation fluid-receiving fluid passage portion ofthe formation fluid-receiving conduit portion of the production tubular,prior to being received by the prime mover, and the formation fluidflowing through the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by at least the sealing engagement between thesealing surface of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular, wherein, while the flowing of thereceived formation fluid is being directed through the gas separatorannulus, the at least a fraction of the entrained gaseous materialbecomes separated, in response to buoyancy forces, from the receivedformation fluid that is being directed through the gas separatorannulus.

In another aspect there is provided a process for effecting productionof formation fluids from a subterranean formation, comprising:

positioning a wellbore tubular within a wellbore, wherein the wellboretubular includes a receptacle portion, wherein the receptacle portionincludes a receptacle sealing surface;providing a production tubular, wherein the production tubular includes:

a formation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing member-engaging surface portion;

a gas separator portion;

a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and

a prime mover disposed for inducing flow of the formation fluid from asubterranean formation and into the formation fluid-receiving fluidpassage portion, and for receiving and energizing the gaseousmaterial-depleted formation fluid to flow through the gaseousmaterial-depleted formation fluid conducting-fluid passage portion tothe surface;

anda sealing member disposable between the sealing member-engaging surfaceportion and the receptacle sealing surface for effecting a seal betweenat least the sealing member-engaging surface portion and the receptaclesealing surface, for preventing, or substantially preventing, flow ofthe formation fluid between at least the sealing member-engaging surfaceportion and the receptacle sealing surface;wherein, while the production tubular is positioned within the wellboretubular such that the seal between at least the sealing member-engagingsurface portion and the receptacle sealing surface is being effected,the gas separator portion is configured to co-operate with at least thewellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid;and wherein the co-operation between the gas separator portion and atleast the wellbore tubular is with effect that, while the flow of theformation fluid is being induced by the prime mover and received throughthe formation fluid-receiving fluid passage portion, flowing of thereceived formation fluid is directed through a gas separator annulusdisposed between the gas separator portion and the wellbore tubular, ina direction opposite to that which the formation fluid is flowing whilebeing received by the formation fluid-receiving fluid passage portion ofthe formation fluid-receiving conduit portion of the production tubular,prior to being received by the prime mover, and the formation fluidflowing through the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by the effected seal between at least the sealingmember-engaging surface portion of the formation fluid-receiving conduitportion of the production tubular and the receptacle sealing surface ofthe receptacle portion of the wellbore tubular, wherein, while theflowing of the received formation fluid is being directed through thegas separator annulus, the at least a fraction of the entrained gaseousmaterial becomes separated, in response to buoyancy forces, from thereceived formation fluid that is being directed through the gasseparator annulus, and the receptacle sealing surface is disposed lessthan a distance “D” of 2.5 millimetres from the sealing member-engagingsurface portion.positioning the production tubular within the wellbore tubular such thatthe seal between at least the sealing member-engaging surface portionand the receptacle sealing surface is being effected;inducing flow of the formation fluid, from a treated subterraneanformation to the formation fluid-receiving fluid passage portion of theformation fluid-receiving conduit portion of the production tubular, bythe prime mover;directing flow of the received formation fluid through the gas separatorannulus, in a direction opposite to that which the formation fluid isflowing while being received by the formation fluid-receiving fluidpassage portion of the formation fluid-receiving conduit portion of theproduction tubular, by the co-operating of the gas separator with thewellbore tubular;preventing, or substantially preventing, the received formation fluid,that is flowing through the gas separator annulus, from returning to theformation fluid-receiving fluid passage portion of the formationfluid-receiving conduit portion of the production tubular by the sealeffected between at least the seal member-engaging sealing surfaceportion of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular;while the flow of the received formation fluid is being directed throughthe gas separator annulus, effecting separation, in response to buoyancyforces, of at least a fraction of gaseous material entrained within theformation fluid flow being flowed through the gas separator annulus togenerate a gaseous material-depleted formation fluid flow;energizing the gaseous material-depleted formation fluid flow with theprime mover for flow to the surface through the gaseousmaterial-depleted fluid formation conduit of the production tubular; andconducting the energized gaseous material-depleted formation fluid flowto the surface through the gaseous material-depleted fluid formationconduit of the production tubular.

In another aspect there is provided a process for effecting productionof formation fluids from a subterranean formation, comprising:

positioning a wellbore tubular within a wellbore, wherein the wellboretubular includes:

a casing string;

a liner string, coupled to the casing string, the liner stringincluding:

-   -   a polished bore receptacle that includes a receptacle portion,        wherein the receptacle portion includes a receptacle sealing        surface; and    -   a sealing surface, sealingly engaged to the casing string for        preventing, or substantially preventing, flow of formation fluid        between the sealing surface and the casing string;        providing a production tubular, wherein the production tubular        includes:

a formation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing surface disposable for sealing engagement withthe receptacle sealing surface for preventing, or substantiallypreventing, flow of the formation fluids between the sealing surface andthe receptacle sealing surface;

a gas separator portion;

a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and

a prime mover disposed for inducing flow of the formation fluid from asubterranean formation and into the formation fluid-receiving fluidpassage portion, and for receiving and energizing the gaseousmaterial-depleted formation fluid to flow through the gaseousmaterial-depleted formation fluid conducting-fluid passage portion tothe surface;

wherein, while the production tubular is positioned within the wellboretubular such that the sealing engagement between at least the sealingsurface of the formation fluid-receiving conduit portion and thereceptacle sealing surface of the receptacle portion is being effected,the gas separator portion is configured to co-operate with at least thewellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid;and wherein the co-operation between the gas separator portion and atleast the wellbore tubular is with effect that, while the flow of theformation fluid is being induced by the prime mover and received throughthe formation fluid-receiving fluid passage portion, flowing of thereceived formation fluid is directed through a gas separator annulusdisposed between the gas separator portion and the wellbore tubular, ina direction opposite to that which the formation fluid is flowing whilebeing received by the formation fluid-receiving fluid passage portion ofthe formation fluid-receiving conduit portion of the production tubular,prior to being received by the prime mover, and the formation fluidflowing through the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by the sealing engagement between at least thesealing surface of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular, wherein, while the flowing of thereceived formation fluid is being directed through the gas separatorannulus, the at least a fraction of the entrained gaseous materialbecomes separated, in response to buoyancy forces, from the receivedformation fluid that is being directed through the gas separatorannulus;positioning the production tubular within the wellbore tubular such thatthe sealing engagement between at least the sealing surface of theformation fluid-receiving conduit portion of the production tubular andthe receptacle sealing surface of the receptacle portion of the wellboretubular is being effected;inducing flow of the formation fluid, from a treated subterraneanformation to the formation fluid-receiving fluid passage portion of theformation fluid-receiving conduit portion of the production tubular, bythe prime mover;directing flow of the received formation fluid through the gas separatorannulus, in a direction opposite to that which the formation fluid isflowing while being received by the formation fluid-receiving fluidpassage portion of the formation fluid-receiving conduit portion of theproduction tubular, by the co-operating of the gas separator with thewellbore tubular;preventing, or substantially preventing, the received formation fluid,that is flowing through the gas separator annulus, from returning to theformation fluid-receiving fluid passage portion of the formationfluid-receiving conduit portion of the production tubular by the sealingengagement between at least the sealing surface of the formationfluid-receiving conduit portion of the production tubular and thereceptacle portion of the wellbore tubular;while the flow of the received formation fluid is being directed throughthe gas separator annulus, effecting separation, in response to buoyancyforces, of at least a fraction of gaseous material entrained within theformation fluid flow being flowed through the gas separator annulus togenerate a gaseous material-depleted formation fluid flow;energizing the gaseous material-depleted formation fluid flow with theprime mover for flow to the surface through the gaseousmaterial-depleted fluid formation conduit of the production tubular; andconducting the energized gaseous material-depleted formation fluid flowto the surface through the gaseous material-depleted fluid formationconduit of the production tubular.

In another aspect there is provided a process for effecting productionof formation fluids from a subterranean formation, comprising:

positioning a wellbore tubular within a wellbore, wherein the wellboretubular includes a casing, wherein the casing includes a receptacleportion, wherein the receptacle portion is defined by an inwardlyextending protrusion of the casing and includes a receptacle sealingsurface;providing a production tubular, wherein the production tubular includes:

a formation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing surface disposable for sealing engagement withthe receptacle sealing surface for preventing, or substantiallypreventing, flow of the formation fluids between the sealing surface andthe receptacle sealing surface;

a gas separator portion;

a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and

a prime mover disposed for inducing flow of the formation fluid from asubterranean formation and into the formation fluid-receiving fluidpassage portion, and for receiving and energizing the gaseousmaterial-depleted formation fluid to flow through the gaseousmaterial-depleted formation fluid conducting-fluid passage portion tothe surface;

wherein, while the production tubular is positioned within the wellboretubular such that the sealing engagement between at least the sealingsurface of the formation fluid-receiving conduit portion and thereceptacle sealing surface of the receptacle portion is being effected,the gas separator portion is configured to co-operate with at least thewellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid;and wherein the co-operation between the gas separator portion and atleast the wellbore tubular is with effect that, while the flow of theformation fluid is being induced by the prime mover and received throughthe formation fluid-receiving fluid passage portion, flowing of thereceived formation fluid is directed through a gas separator annulusdisposed between the gas separator portion and the wellbore tubular, ina direction opposite to that which the formation fluid is flowing whilebeing received by the formation fluid-receiving fluid passage portion ofthe formation fluid-receiving conduit portion of the production tubular,prior to being received by the prime mover, and the formation fluidflowing through the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by the sealing engagement between at least thesealing surface of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular, wherein, while the flowing of thereceived formation fluid is being directed through the gas separatorannulus, the at least a fraction of the entrained gaseous materialbecomes separated, in response to buoyancy forces, from the receivedformation fluid that is being directed through the gas separatorannulus;positioning the production tubular within the wellbore tubular such thatthe sealing engagement between at least the sealing surface of theformation fluid-receiving conduit portion of the production tubular andthe receptacle sealing surface of the receptacle portion of the wellboretubular is being effected;inducing flow of the formation fluid, from a treated subterraneanformation to the formation fluid-receiving fluid passage portion of theformation fluid-receiving conduit portion of the production tubular, bythe prime mover;directing flow of the received formation fluid through the gas separatorannulus, in a direction opposite to that which the formation fluid isflowing while being received by the formation fluid-receiving fluidpassage portion of the formation fluid-receiving conduit portion of theproduction tubular, by the co-operating of the gas separator with thewellbore tubular;preventing, or substantially preventing, the received formation fluid,that is flowing through the gas separator annulus, from returning to theformation fluid-receiving fluid passage portion of the formationfluid-receiving conduit portion of the production tubular by the sealingengagement between at least the sealing surface of the formationfluid-receiving conduit portion of the production tubular and thereceptacle portion of the wellbore tubular;while the flow of the received formation fluid is being directed throughthe gas separator annulus, effecting separation, in response to buoyancyforces, of at least a fraction of gaseous material entrained within theformation fluid flow being flowed through the gas separator annulus togenerate a gaseous material-depleted formation fluid flow;energizing the gaseous material-depleted formation fluid flow with theprime mover for flow to the surface through the gaseousmaterial-depleted fluid formation conduit of the production tubular; andconducting the energized gaseous material-depleted formation fluid flowto the surface through the gaseous material-depleted fluid formationconduit of the production tubular.

BRIEF DESCRIPTION OF DRAWINGS

The preferred embodiments will now be described with the followingaccompanying drawings, in which:

FIG. 1 is a schematic illustration of an embodiment of the presentdisclosure, illustrating fluid flowpath through the gas separator;

FIG. 2 is a schematic illustration of an enlarged portion of theembodiment illustrated in FIG. 1, in the region of the gas separator;

FIG. 2A is a schematic illustration of a further enlarged portion of theembodiment illustrated in FIG. 1, in the region of the gas separator,and specifically illustrating the relative spatial disposition between areceptacle sealing surface of the wellbore tubular and the sealingmember-engaging surface portion of the production tubular;

FIG. 3 is a schematic illustration of another embodiment of the presentdisclosure, also illustrating fluid flowpath through the gas separator;and

FIG. 4 is a schematic illustration of an enlarged portion of theembodiment illustrated in FIG. 1, in the region of the gas separator.

DETAILED DESCRIPTION

The term “upwardly” means, in a spatial context, from a lower positionto an upper position. The lower and upper positions do not necessarilyneed to be in perfect vertical alignment, but this possibility is notexcluded.

The term “downardly” means, in a spatial context, from an upper positionto a lower position. The upper and lower position do not necessarilyneed to be in perfect vertical alignment, but this possibility is notexcluded.

The term “tubular” refers to any generally tubular conduit (notnecessarily cylindrical in cross-section) for transporting fluid, intoor from a subterranean formation. A “tubular”, as deployed in awellbore, may be formed from individual, discrete lengths of generallytubular conduit that are joined together to form, for example a tubingstring, drill string, casing string, or liner. In this respect, atubular may be a tubing string, drill string, casing string, or liner.Any of these structures are positioned within a wellbore and utilized,at least in part, to transport fluids. The tubular may have a bore of agenerally uniform diameter throughout the length thereof or may have twoor more sections having bores of different diameters. In someembodiments, for example, one or more downhole tools may be secured tothe tubular.

“Formation fluid” is fluid that is contained within a subterraneanformation. Formation fluid may be liquid material, gaseous material, ora mixture of liquid material and gaseous material. In some embodiments,for example, the formation fluid includes hydrocarbonaceous material,such as oil, natural gas, or combinations thereof.

Referring to FIGS. 1 to 4, there is provided a system 10 for effectingproduction of formation fluids from a subterranean formation 50. Thesystem includes a wellbore tubular 20 and a production tubular 30. Thewellbore tubular 20 and the production tubular 30 extend from a wellhead15 that is supported on the ground surface 16.

The wellbore tubular 20 is disposed or positioned within a wellbore 40.The wellbore tubular 20 includes a receptacle portion 22. The receptacleportion 22 includes a receptacle sealing surface 21.

The wellbore 40 can be straight, curved, or branched. The wellbore canhave various wellbore portions. A wellbore portion is an axial length ofa wellbore. A wellbore portion can be characterized as “vertical” or“horizontal” even though the actual axial orientation can vary from truevertical or true horizontal, and even though the axial path can tend to“corkscrew” or otherwise vary. The term “horizontal”, when used todescribe a wellbore portion, refers to a horizontal or highly deviatedwellbore portion as understood in the art, such as, for example, awellbore portion having a longitudinal axis that is between 70 and 110degrees from vertical.

In some embodiments, for example, the wellbore tubular 20 includes acasing. The casing isolates certain zones of the subterranean formation50 from the formation fluid being produced from another zone of thesubterranean formation. In some embodiments, for example, the casingstabilizes the subterranean formation during drilling of the wellbore,as well as after the wellbore has been completed, by preventing thecollapse of the subterranean formation that is defining the wellbore.

In some embodiments, for example, the casing 20 includes one or morecasing strings, each of which is positioned within the well bore, havingone end extending from the well head, either surface or subsea. Thecasing strings may be cemented to the wellbore. The combination ofcement and casing strengthens the wellbore and facilitates the isolationof certain areas of the subterranean formation behind the casing for theproduction of formation fluids. In some embodiments, for example andreferring to FIG. 1, the casing, including one or more casing strings,is connected at its other end to a liner string 26. The liner stringextends only a short distance above the lower end of the previouslyinstalled casing string and is suspended within the wellbore by a linerhanger connected to the previously installed casing string. The linerstring can be made from the same material as the casing string, but,unlike the casing string, the liner string does not extend back to thewellhead. The liner string may be cemented to the wellbore, or remainuncemented.

In some embodiments, for example and referring to FIGS. 3 and 4, thecasing may include one or more expandable liner strings. During assemblyof the casing, and after being disposed in the wellbore, the expandableliner string is expanded diametrically into frictional engagement withthe previous string of casing or liner (which could also have beenexpanded diametrically into frictional engagement with a furtherprevious string of casing or liner). The expanded string may be cementedto the wellbore, or remain uncemented. The assembly of the casing, usingsuch expandable liner strings, effects production of at least a casingsection generally described as a “monobore” casing or casing section.

In some embodiments, for example, the production tubular may be atubular string that includes several “joints” (a “joint” is a length ofpipe) or other tubular members assembled to create the string.

The production tubular 30 is disposed within the wellbore tubular 20.The production tubular includes a formation fluid-receiving conduitportion 32, a gas separator portion 38, a gaseous material-depletedfluid formation conduit portion 34, and a prime mover 36.

The formation fluid-receiving conduit portion 32 includes a formationfluid-receiving fluid passage-defining surface 323 that defines aformation fluid-receiving fluid passage portion 3231 for receiving theformation fluid.

In one aspect, the formation fluid-receiving conduit portion includes asealing surface 321 disposed in sealing engagement with the receptaclesealing surface 21 for preventing, or substantially preventing, flow ofthe formation fluids between the sealing surface 321 and the receptaclesealing surface 21. The sealing engagement effects a seal between thesealing surface 321 and the receptacle sealing surface 21. In someembodiments, for example, one of the sealing surfaces 21 or 321 isdefined by a sealing member 400 that is disposed between the formationfluid-receiving conduit portion 32 and the receptacle portion 22 foreffecting the seal between the formation fluid-receiving conduit portion32 and the receptacle portion 22.

In some embodiments, for example, the sealing member 400 includesresilient material, such as elastomeric material. In some embodiments,for example, the sealing member 400 includes deformable metallicmaterials.

The gas separator portion 38 is configured to co-operate with at leastthe wellbore tubular 20 for effecting separation of at least a fractionof gaseous material, that is entrained within the received formationfluid, from the received formation fluid to generate a gaseousmaterial-depleted formation fluid.

The gaseous material-depleted fluid formation conduit portion 34 definesa gaseous material-depleted formation fluid conducting-fluid passageportion 341 for conducting a flow of the gaseous material-depletedformation fluid to the surface.

The prime mover 36 is disposed for inducing flow of the formation fluidfrom a subterranean formation and into the formation fluid-receivingfluid passage portion 3231, and for receiving and energizing the gaseousmaterial-depleted formation fluid to flow through the gaseousmaterial-depleted formation fluid conducting-fluid passage portion 341to the surface. In some embodiments, for example, the prime mover 36 isa fluid propeller. In some of these embodiments, for example, the primemover is a pump, such as a downhole pump. In some embodiments, forexample, the pump is a rod pump, such as a sucker rod pump.

The co-operation between the gas separator portion 38 and at least thewellbore tubular 20 is with effect that, while the flow of the formationfluid is being induced by the prime mover 36 and received through theformation fluid-receiving fluid passage portion 3231, flowing of thereceived formation fluid is directed through a gas separator annulus 381disposed between the gas separator portion 38 and the wellbore tubular20, in a direction opposite to that which the formation fluid is flowingwhile being received by the formation fluid-receiving fluid passageportion 3231 of the formation fluid-receiving conduit portion 32 of theproduction tubular 30, prior to being received by the prime mover 36,and the formation fluid flowing through the gas separator annulus 381 isprevented, or substantially prevented, from returning to the formationfluid-receiving fluid passage portion 3231 of the formationfluid-receiving conduit portion 32 of the production tubular 30 by atleast the seal formed (as above-described) between the formationfluid-receiving conduit portion 32 of the production tubular 30 and thereceptacle portion 22 of the wellbore tubular 20, wherein, while theflowing of the received formation fluid is being directed through thegas separator annulus 381, the at least a fraction of the entrainedgaseous material becomes separated, in response to buoyancy forces, fromthe received formation fluid that is being directed through the gasseparator annulus 381.

Referring to FIG. 2A, in another aspect, the formation fluid-receivingconduit portion 32 includes a sealing member-engaging surface portion325, and a sealing member 400 is disposed between a sealingmember-engaging surface portion 325 of the formation fluid-receivingconduit portion 32 and the receptacle sealing surface 21 for effectingthe seal between at least the sealing member-engaging surface portion325 and the receptacle sealing surface 21, for preventing, orsubstantially preventing, flow of the formation fluid between at leastthe sealing member-engaging surface portion 325 and the receptaclesealing surface 21. In some of these embodiments, for example, thesealing member 400 is coupled to, or carried, by the formationfluid-receiving conduit portion 32. The receptacle sealing surface 21 isdisposed less than a distance “D” of 2.5 millimetres from the sealingmember-engaging surface portion 325. In some embodiments, for example,the distance “D” is one (1) millimetre, such that the receptacle sealingsurface 21 is disposed less than one (1) millimetre from the sealingmember-engaging surface portion 325. This distance “D” is selected so asto minimize debris accumulation but still permit the in installation ofthe sealing member 400.

By effecting separation of at least a fraction of gaseous material, thatis entrained within the received flow of formation fluid, from thereceived formation fluid, the gas lock phenomena is at least partiallymitigated by the co-operation of the gas separator 38 and the wellboretubular 20. Unlike existing packer-type gas anchors, by co-operativelyconfiguring the wellbore tubular 20 and the production tubular 30 suchthat the provided spacing between the receptacle sealing surface 21, ofthe wellbore tubular 20, and the sealing member-engaging surface portion325, of the production tubular 30, is below a predetermined distance (asdefined above), the amount of space to be dedicated for effecting thesealing engagement between the receptacle sealing surface 21 and thesealing member-engaging surface portion 325 can be minimized such thatconventional packers are not required to be used associated with the gasseparator portion 38 to effect the necessary sealing for preventing, orsubstantially preventing flow between the tubulars 20, 30 in order forthe removal of the entrained gases to be effected. Because this is thecase, the problem of debris accumulation on the packer, which wouldotherwise make it more difficult to remove the production tubular 30,from the wellbore tubular 20, owing to the fact that such accumulateddebris may cause the packer associated with a gas separator, disposed onthe production tubular 30, to be stuck against the wellbore tubular 20,is eliminated or mitigated, at least as it relates to its relevance toremovability of the production tubular 30 from the wellbore, such asduring workovers.

In some embodiments, for example, the production tubular 30 isreleasably secured to the wellbore tubular 20. In some of theseembodiments, for example, the production tubular is disposed in aninterference fit relationship (such as a press-fit relationship) withthe wellbore tubular 20. In some of these embodiments, for example, theinterference fit relationship is effected between the sealing surface321 of the formation fluid-receiving conduit portion 32 of theproduction tubular 30 and the receptacle sealing surface 21 of thereceptacle portion 22 of the wellbore tubular 20.

Referring to FIGS. 1 and 2, in some embodiments, for example, thewellbore tubular 20 includes a casing 2, and the casing includes acasing string 201 and a liner string 26. In some embodiments, forexample, the liner string 26 is hung from the casing string 201. Theliner string 26 includes a polished bore receptacle 261 and an externalsealing surface 262. The polished bore receptacle 261 includes thereceptacle portion 22. The external sealing surface 262 is sealinglyengaged to the casing string 201 for preventing, or substantiallypreventing, flow of formation fluid between the external sealing surface262 and the casing string 201. In some embodiments, for example, thesealing engagement between the surface 262 and the casing string 201 iseffected by a packer 24 mounted to the casing string 201. The productiontubular 30 is disposed within the polished bore receptacle 261, andurging of the sealing engagement between the sealing surface 321 of theproduction tubular 30 and the receptacle sealing surface 21 of thereceptacle portion 22 of the polished bore receptacle 261 is effectedwith a seal latch assembly that releasably secures the productiontubular 30 to the polished bore receptacle 261. In some embodiments, forexample, the production tubular 30 is releasably coupled or releasablysecured to the polished bore receptacle 261. In some of theseembodiments, for example, the releasable coupling (or the releasablesecurement) is effected by way of an interference fit engagement (suchas a press-fit engagement) between the production tubular 30 and thereceptacle portion 22 of the polished bore receptacle 261.

Referring to FIGS. 3 and 4, in some embodiments, for example, thewellbore tubular 20 includes a casing 2, and the receptacle portion 22extends inwardly from the casing 2. In some embodiments, for example,the receptacle portion 22 defines a constricted portion 221 of thecasing 2. In some embodiments, for example, the production tubular 30 isreleasably coupled or releasably secured to the receptacle portion 22.In some of these embodiments, for example, the releasable coupling (orthe releasable securement) is effected by way of an interference fitengagement (such as a press-fit engagement) between the productiontubular 30 and the receptacle portion 22. In this respect, the extendinginward receptacle portion 22 is permanently affixed to the casing 2,thus any accumulation of debris will not prevent removal of theproduction tubular 30 and the sealing member-engaging surface portion325.

In some embodiments, for example, the system further includes aconducting annulus 382 disposed between the production tubular 30 andthe wellbore tubular 20. The conducting annulus 382 is configured toreceive and conduct the separated gaseous material to the surface. Thegas separator annulus 381 is disposed in vertical alignment with theconducting annulus 382.

In some embodiments, for example, the gas separator 38 furtherco-operates with the wellbore tubular 20 with effect that the receivedformation fluid flow being flowed through the gas separator annulus 381is flowing in a downwardly direction.

In some embodiments, for example, the disposition of the wellboretubular 20 relative to the wellbore is with effect that the effectedfluid communication between the formation fluid-receiving fluid passageportion 3231 of the production tubular 30 and the subterranean formationtreatment zone is isolated, or substantially isolated, from at least oneother zone of the subterranean formation (such as, in FIG. 1, by anotherpacker 501).

In some embodiments, for example, the prime mover 36 is disposed withina horizontal wellbore portion of the wellbore 40.

In some embodiments, for example, a mechanical filter 327 (such as asand screen) is disposed within the production tubular 30, upstream ofthe gas separator 38 for filtering solids from the formation fluid whoseflow has been induced into the formation fluid-receiving conduit portion32. Intermittently, the solids, retained by the mechanical filter 327can be purged by pumping a fluid downhole through the annulus 382.

In some of these embodiments, for example, a check valve may be disposedwithin the production tubular, upstream of the inlet, for enabling fluidcirculation of a purging fluid that may be used for cleaning out debriswithin the production tubular, while preventing fluid communication withthe production zone.

There is also provided a process for effecting production of formationfluids from a subterranean formation.

The process includes positioning the wellbore tubular 20 within thewellbore, and then positioning the production tubular 30 within thewellbore tubular 20.

Flow of the formation fluid, from a treated subterranean formation 50 tothe formation fluid-receiving conduit portion 32 of the productiontubular 30, is then induced by the prime mover 36. The flow of thereceived formation fluid is directed through the gas separator annulus381, in a direction opposite to that which the formation fluid isflowing while being received by the formation fluid-receiving fluidpassage portion 3231 of the production tubular 30, by the co-operatingof the gas separator 38 with the wellbore tubular 20. The receivedformation fluid, that is flowing through the gas separator annulus 381,is prevented, or substantially prevented, from returning to theformation fluid-receiving fluid passage portion 3231 of the productiontubular 30 by at least the sealing engagement between the formationfluid-receiving fluid passage portion 3231 of the formationfluid-receiving conduit portion 32 of the production tubular 30 and thereceptacle sealing surface 21 of the receptacle portion 22 of thewellbore tubular 20. While the flow of the received formation fluid isbeing directed through the gas separator annulus 381, separation, of atleast a fraction of gaseous material entrained within the formationfluid flow being flowed through the gas separator annulus 381, inresponse to buoyancy forces, is effected to generate a gaseousmaterial-depleted formation fluid flow. The gaseous material-depletedformation fluid flow is energized with the prime mover 36 for flow tothe surface through the gaseous material-depleted formation fluidconducting-fluid passage portion 341 of the production tubular 30. Theenergized gaseous material-depleted formation fluid flow is conducted tothe surface through the gaseous material-depleted formation fluidconducting-fluid passage portion 341.

In some embodiments, for example, the received formation fluid flow,being flowed through the gas separator annulus 381, is flowing, in adownwardly direction.

In some embodiments, for example, while the flow of the formation fluid,for receiving by the formation fluid-receiving fluid passage portion3231 of the production tubular 30, is being induced, the formation fluidis flowing in an upwardly direction.

In some embodiments, for example, the inducing flow of formation fluidincludes effecting the development of a sufficient pressuredifferential, between the suction of the prime mover 36 and thesubterranean formation 50, by the prime mover 36.

In some embodiments, for example, the positioning of the productiontubular 30 includes positioning the prime mover 36 within a horizontalwellbore portion of the wellbore 40.

In some embodiments, for example, the process further includes flowingthe separated gaseous material to the surface through a conductingannulus 382 disposed between the production tubular 30 and the wellboretubular 20. In some of these embodiments, for example, the gas separatorannulus 381 is disposed in vertical alignment with the conductingannulus 382. In some of these embodiments, for example, the flowing ofthe separated gaseous material is in a direction opposite to that of theflow of the received formation fluid through the gas separator annulus381.

In some embodiments, for example, the process further includes, prior tothe positioning of a production tubular 30 within the wellbore tubular20, the steps of: delivering a wellbore treatment fluid to a treatmentzone of the subterranean formation 50 to effect treatment of thesubterranean formation treatment zone, and then suspending thedelivering of the wellbore treatment fluid. The formation fluid isderived from the subterranean formation treatment zone. In some of theseembodiments, the process further includes, prior to the delivering ofthe wellbore treatment fluid to the subterranean formation treatmentzone, the step of positioning the wellbore treatment tubular into fluidcommunication with the subterranean formation treatment zone with effectthat the wellbore treatment tubular is disposed for conducting wellboretreatment fluid to the subterranean formation treatment zone, and alsofurther includes, after the delivering of the wellbore treatment fluid,repositioning the wellbore treatment tubular with effect that fluidcommunication between the wellbore treatment tubular and the receptacleportion becomes suspended. After the repositioning, the productiontubular 30 is positioned within the wellbore tubular 20.

“Wellbore treatment fluid” refers to fluid used in treatment (such asstimulation) of a subterranean formation. Stimulation is a type oftreatment performed on a subterranean formation to restore or enhancethe productivity of oil or gas or other fluid within the subterraneanformation. Stimulation includes hydraulic fracturing. Nonlimitingexamples of a suitable wellbore servicing fluid include but are notlimited to a fracturing fluid, a perforating or hydrajetting fluid, anacidizing fluid, or combinations thereof.

In some embodiments, for example, while the delivering of the wellboretreatment fluid is being effected, the receptacle 22 is sealinglyengaging the wellbore treatment tubular.

The wellbore treatment tubular includes a fluid passage for conductingwellbore treatment fluid from a wellbore treatment fluid supply sourcedisposed on the surface to the subterranean formation 50. In someembodiments, for example, The wellbore treatment tubular may be atubular string that includes several “joints” (a “joint” is a length ofpipe) or other tubular members assembled to create the string. In someembodiments, for example, the wellbore treatment tubular includes one ormore downhole tools for effecting fracturing of the subterraneanformation with which the one or more downhole tools is disposed infracture-effecting communication with when disposed within the wellbore.

One or more flow control devices may be provided for selectivelyeffecting fluid communication between the receptacle portion and asubterranean formation. In some modes of operation, the effecting offluid communication between the wellbore treatment tubular and atreatment zone of a subterranean formation 50, by the one or more flowcontrol valves, provides a flowpath for the delivery of wellboretreatment fluid. In other modes of operation, the effecting of fluidcommunication between the formation fluid-receiving fluid passageportion 3231 of the production tubular 30 and a subterranean formation,by the one or more flow control valves, provides a flowpath forconducting of formation fluid from the subterranean formation to theproduction tubular 30.

In some embodiments, for example, the one or more flow control devicesare integrated within the wellbore tubular 20. For those embodimentswhere the one or more flow control devices are provided by the wellboretubular, in some of these embodiments, for example, the wellboretreatment tubular includes a tool for selectively effecting opening andclosing of the one or more flow control devices integrated within thewellbore tubular for effecting fluid communication between a selectedzone of the subterranean formation 50 and the wellbore treatmenttubular, and thereby facilitating the delivery of the wellbore treatmentfluid to the selected zone of the subterranean formation 50 to effecttreatment of the selected zone of the subterranean formation,independently of other zones of the subterranean formation. Also forthose embodiments where the one or more flow control devices areprovided by the wellbore tubular, in some of these embodiments, forexample, the production tubular 30 includes a tool for selectivelyeffecting opening and closing of the one or more flow control devicesintegrated within the wellbore tubular for effecting fluid communicationbetween a selected zone of the treated subterranean formation 50 and theformation fluid-receiving fluid passage portion 3231 of the productiontubular 30, while isolating other ones of the zones of the treatedsubterranean formation, and thereby facilitating flow of the formationfluid from the selected zone of the treated subterranean formation, tothe formation fluid-receiving fluid passage portion 3231, whileisolating other ones of the zones of the treated subterranean formationfrom the formation fluid being flowed from the selected zone.

The flow control devices may comprise sliding sleeves, valves, and othertypes of flow control devices which may be actuated by a member droppeddown through the associated tubular.

In the above description, for purposes of explanation, numerous detailsare set forth in order to provide a thorough understanding of thepresent disclosure. However, it will be apparent to one skilled in theart that these specific details are not required in order to practicethe present disclosure. Although certain dimensions and materials aredescribed for implementing the disclosed example embodiments, othersuitable dimensions and/or materials may be used within the scope ofthis disclosure. All such modifications and variations, including allsuitable current and future changes in technology, are believed to bewithin the sphere and scope of the present disclosure. All referencesmentioned are hereby incorporated by reference in their entirety.

1. A system for effecting production of formation fluid from asubterranean formation, comprising: a wellbore tubular disposed within awellbore, wherein the wellbore tubular includes a receptacle portion,wherein the receptacle portion includes a receptacle sealing surface; aproduction tubular, disposed within the wellbore tubular, including: aformation fluid-receiving conduit portion, defining a formationfluid-receiving fluid passage portion for receiving the formation fluid,and including a sealing member-engaging surface portion; a gas separatorportion configured to co-operate with at least the wellbore tubular foreffecting separation of at least a fraction of gaseous material, that isentrained within the received formation fluid, from the receivedformation fluid to generate a gaseous material-depleted formation fluid;a gaseous material-depleted fluid formation conduit defining a gaseousmaterial-depleted formation fluid conducting-fluid passage portion forconducting a flow of the gaseous material-depleted formation fluid tothe surface; and a prime mover disposed for inducing flow of theformation fluid from a subterranean formation and into the formationfluid-receiving fluid passage portion, and for receiving and energizingthe gaseous material-depleted formation fluid to flow through thegaseous material-depleted formation fluid conducting-fluid passageportion to the surface; and a sealing member disposed between thesealing member-engaging surface portion and the receptacle sealingsurface for effecting a seal between at least the sealingmember-engaging surface portion and the receptacle sealing surface, forpreventing, or substantially preventing, flow of the formation fluidbetween at least the sealing member-engaging external surface portionand the receptacle sealing surface; wherein the co-operation between thegas separator portion and at least the wellbore tubular is with effectthat, while the flow of the formation fluid is being induced by theprime mover and received through the formation fluid-receiving fluidpassage portion, flowing of the received formation fluid is directedthrough a gas separator annulus disposed between the gas separatorportion and the wellbore tubular, in a direction opposite to that whichthe formation fluid is flowing while being received by the formationfluid-receiving fluid passage portion of the formation fluid-receivingconduit portion of the production tubular, prior to being received bythe prime mover, and the formation fluid flowing through the gasseparator annulus is prevented, or substantially prevented, fromreturning to the formation fluid-receiving fluid passage portion of theformation fluid-receiving conduit portion of the production tubular bythe effected seal between at least the sealing member-engaging surfaceportion of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular, wherein, while the flowing of thereceived formation fluid is being directed through the gas separatorannulus, the at least a fraction of the entrained gaseous materialbecomes separated, in response to buoyancy forces, from the receivedformation fluid that is being directed through the gas separatorannulus; and wherein the receptacle sealing surface is disposed lessthan a distance “D” of 2.5 millimetres from the sealing member-engagingsurface portion.
 2. The system as claimed in claim 1; wherein thewellbore tubular includes a casing, and the receptacle portion isdefined by an inwardly extending protrusion of the casing.
 3. The systemas claimed in claim 1; wherein the wellbore tubular includes: a casingstring; a liner string, coupled to the casing string, the liner stringincluding: a polished bore receptacle that includes the receptacleportion; and a sealing surface, sealingly engaged to the casing stringfor preventing, or substantially preventing, flow of formation fluidbetween the sealing surface and the casing string; and wherein theproduction tubular is disposed within the polished bore receptacle. 4.The system as claimed in claim 3; wherein the coupling of the linerstring to the casing string is by way of hanging of the liner string tothe casing string.
 5. The system as claimed in claim 3; wherein thesealing member is disposed in sealing engagement with both of thesealing member-engaging surface portion and the receptacle sealingsurface, and urging of the sealing engagement is effected with a seallatch assembly.
 6. The process as claimed in claim 3; wherein the casingstring includes a packer for effecting the sealing engagement betweenthe sealing surface of the liner string and the casing string.
 7. Thesystem as claimed in claim 1; further comprising: a conducting annulusdisposed between the production tubular and the wellbore tubular andconfigured to receive and conduct the separated gaseous material to thesurface; wherein the gas separator annulus is disposed in verticalalignment with the conducting annulus.
 8. The system as claimed in claim1; wherein the gas separator further co-operates with the wellboretubular with effect that the received formation fluid flow being flowedthrough the gas separator annulus is flowing in a downwardly direction.9. The system as claimed in claim 1; wherein the disposition of thewellbore tubular relative to the wellbore is with effect that theeffected fluid communication between the formation fluid-receiving fluidpassage portion of the production tubular and the subterranean formationtreatment zone is isolated, or substantially isolated, from at least oneother zone of the subterranean formation.
 10. The system as claimed inclaim 1; wherein the prime mover is disposed within a horizontalwellbore portion of the wellbore.
 11. The system as claimed in claim 1;wherein the production tubular is releasably secured to the wellboretubular.
 12. The system as claimed in claim 1; wherein the productiontubular is disposed in an interference fit relationship with thewellbore tubular.
 13. The system as claimed in claim 1; wherein thesealing member is coupled to the production tubular.
 14. The system asclaimed in claim 1; wherein the sealing member is carried by theproduction tubular.
 15. A system for effecting production of formationfluids from a subterranean formation, comprising: a wellbore tubulardisposed within a wellbore, wherein the wellbore tubular includes: acasing string; a liner string, coupled to the casing string, the linerstring including: a polished bore receptacle that includes a receptacleportion, wherein the receptacle portion includes a receptacle sealingsurface; and a sealing surface, sealingly engaged to the casing stringfor preventing, or substantially preventing, flow of formation fluidbetween the sealing surface and the casing string; and a productiontubular, disposed within the wellbore tubular, including: a formationfluid-receiving conduit portion, defining a formation fluid-receivingfluid passage portion for receiving the formation fluid, and including asealing surface disposed in sealing engagement with the receptaclesealing surface for preventing, or substantially preventing, flow of theformation fluids between the sealing surface and the receptacle sealingsurface; a gas separator portion configured to co-operate with at leastthe wellbore tubular for effecting separation of at least a fraction ofgaseous material, that is entrained within the received formation fluid,from the received formation fluid to generate a gaseousmaterial-depleted formation fluid; a gaseous material-depleted fluidformation conduit defining a gaseous material-depleted formation fluidconducting-fluid passage portion for conducting a flow of the gaseousmaterial-depleted formation fluid to the surface; and a prime moverdisposed for inducing flow of the formation fluid from a subterraneanformation and into the formation fluid-receiving fluid passage portion,and for receiving and energizing the gaseous material-depleted formationfluid to flow through the gaseous material-depleted formation fluidconducting-fluid passage portion to the surface; wherein theco-operation between the gas separator portion and at least the wellboretubular is with effect that, while the flow of the formation fluid isbeing induced by the prime mover and received through the formationfluid-receiving fluid passage portion, flowing of the received formationfluid is directed through a gas separator annulus disposed between thegas separator portion and the wellbore tubular, in a direction oppositeto that which the formation fluid is flowing while being received by theformation fluid-receiving fluid passage portion of the formationfluid-receiving conduit portion of the production tubular, prior tobeing received by the prime mover, and the formation fluid flowingthrough the gas separator annulus is prevented, or substantiallyprevented, from returning to the formation fluid-receiving fluid passageportion of the formation fluid-receiving conduit portion of theproduction tubular by at least the sealing engagement between thesealing surface of the formation fluid-receiving conduit portion of theproduction tubular and the receptacle sealing surface of the receptacleportion of the wellbore tubular, wherein, while the flowing of thereceived formation fluid is being directed through the gas separatorannulus, the at least a fraction of the entrained gaseous materialbecomes separated, in response to buoyancy forces, from the receivedformation fluid that is being directed through the gas separatorannulus.
 16. The system as claimed in claim 15; wherein the productiontubular is disposed within the polished bore receptacle, and urging ofthe sealing engagement between the sealing surface of the formationfluid-receiving conduit portion of the production tubular and thereceptacle sealing surface of the receptacle portion of the polishedbore receptacle is effected with a seal latch assembly.
 17. The systemas claimed in claim 15; wherein the coupling of the liner string to thecasing string is by way of hanging of the liner string to the casingstring.
 18. The system as claimed in claim 15; wherein the productiontubular is releasably secured to the wellbore tubular.
 19. The system asclaimed in claim 15; wherein the production tubular is disposed in aninterference fit relationship with the wellbore tubular.
 20. The systemas claimed in claim 19; wherein the interference fit relationship iseffected between the sealing surface of the formation fluid-receivingconduit portion of the production tubular and the receptacle sealingsurface of the receptacle portion of the wellbore tubular.
 21. A systemfor effecting production of formation fluids from a subterraneanformation, comprising: a wellbore tubular disposed within a wellbore,wherein the wellbore tubular includes a casing, wherein the casingincludes a receptacle portion, wherein the receptacle portion is definedby an inwardly extending protrusion of the casing and includes areceptacle sealing surface; and a production tubular, disposed withinthe wellbore tubular, including: a formation fluid-receiving conduitportion, defining a formation fluid-receiving fluid passage portion forreceiving the formation fluid, and including a sealing surface disposedin sealing engagement with the receptacle sealing surface forpreventing, or substantially preventing, flow of the formation fluidsbetween the sealing surface and the receptacle sealing surface; a gasseparator portion configured to co-operate with at least the wellboretubular for effecting separation of at least a fraction of gaseousmaterial, that is entrained within the received formation fluid, fromthe received formation fluid to generate a gaseous material-depletedformation fluid; a gaseous material-depleted fluid formation conduitdefining a gaseous material-depleted formation fluid conducting-fluidpassage portion for conducting a flow of the gaseous material-depletedformation fluid to the surface; and a prime mover disposed for inducingflow of the formation fluid from a subterranean formation and into theformation fluid-receiving fluid passage portion, and for receiving andenergizing the gaseous material-depleted formation fluid to flow throughthe gaseous material-depleted formation fluid conducting-fluid passageportion to the surface; wherein the co-operation between the gasseparator portion and at least the wellbore tubular is with effect that,while the flow of the formation fluid is being induced by the primemover and received through the formation fluid-receiving fluid passageportion, flowing of the received formation fluid is directed through agas separator annulus disposed between the gas separator portion and thewellbore tubular, in a direction opposite to that which the formationfluid is flowing while being received by the formation fluid-receivingfluid passage portion of the formation fluid-receiving conduit portionof the production tubular, prior to being received by the prime mover,and the formation fluid flowing through the gas separator annulus isprevented, or substantially prevented, from returning to the formationfluid-receiving fluid passage portion of the formation fluid-receivingconduit portion of the production tubular by at least the sealingengagement between the sealing surface of the formation fluid-receivingconduit portion of the production tubular and the receptacle sealingsurface of the receptacle portion of the wellbore tubular, wherein,while the flowing of the received formation fluid is being directedthrough the gas separator annulus, the at least a fraction of theentrained gaseous material becomes separated, in response to buoyancyforces, from the received formation fluid that is being directed throughthe gas separator annulus.
 22. The system as claimed in claim 21;wherein the receptacle portion defines a constricted passage within thecasing.
 23. The system as claimed in claim 21; wherein the productiontubular is releasably secured to the wellbore tubular.
 24. The system asclaimed in claim 21; wherein the production tubular is disposed in aninterference fit relationship with the wellbore tubular.
 25. The systemas claimed in claim 24; wherein the interference fit relationship iseffected between the sealing surface of the formation fluid-receivingconduit portion of the production tubular and the receptacle sealingsurface of the receptacle portion of the wellbore tubular. 26-68.(canceled)